Continuous tank furnace



Nov. 22, 1932. E. T. FERNGREQN CONTINUOUS TANK FURNACE Original FiledOct. 27, 1923 2 Sheets-Sheet 1 gwwzntoz I 9 Enoch 7T Fernqmni Nov. 22,1932. FERNGREN 1,888,496

Y CONTINUOUS TANK-FURNACE Original Filed Oct. 27, 1923 2 Sheets-Sheet 2Patented Nov. 22, 1932 UNITED STATES PATENT ore ENOG'H '1. FEBNGBEN, OFTOLEDO, OE' IO, ASSIGNOB TO LIBBEY OWENS EOBD GLASS COHPAHY,'OF TOLEDO,OJHIO, A CORPORATION 01 0510 OON'LINUQUS TANK FURNACE originalapplication med mmav, ma, semi No. 671,128. invites and an; applicationfiled mm as,

1928. Serial No. 97,509. I

This invention relates to improvements in continuous tank furnaces, andmore particularly to such a furnace designed to furnish molten glasssimultaneously to a plurality of 5 sheet glass drawing machines. In theprocess of drawing sheet glass, it has been found more economical tosupply two or more machines from a single furnace, since i a relativelysmall increase in the size of the 13 tank, and the fuel consumption willenlarge its capacity sufliciently to supply the extra machine. In themost approved type of iiurnace now in use, a pair of parallel refiningtanks arranged closely adjacent one another,

13 form prolongations of the single melting tankin which the moltenglass is produced. The flow of molten glass from the melting tank isdivided between the two refining tanks F through which it flows to theseparate drawpots which supply the sheet glass drawing machines. v

in the use of such furnaces it has been found that there is a tendencyfor the hi her M temperatured glass from the melting tanli, to flowalong the inner adjacent sides of the two refining tanks, and coolingtanks, and toward the inner sides of the draw-pots, causing aprogressive stagnation oi the cooler glass in n the outer side of eachdraw-pot, making it necessary to heat this glass to sustain the requiredamount of fluidity tor the drawing operation.

Also there seems to develop a too rapid surface stratum movement oi"glass from the melting tank through each oi the refining tanlrs to thedraw-pot. This excessive surface movement of the glass from the meltingend, which is undoubtedly caused by the heavy derounds of the two sheetdrawing units upon the melting capacity of the tank under'conditionswhich promote a partial stagnation oi": all the other glass whichis notin the path oi thestream movement, will not give the iresh- M ly meltedloath the proper time for settling and'planin This hotter glass, becauseof its greater mo ility, is caused to flow toward the two draw-potsthrough channels formed lay the stream current in the remainder of theglass contained in each refining tanlz, which cooler glass thusfunction's as a sort oi sup porting bed through which a river of more Ifluent glass will flow to supply the demands of the revving-machine.

'Ilhe present improved form of furnace is designed to furnish a moreeven flow of more completely refined glass to each ot' the separatesheet glass producing machines. One obgect of the invention is toprovide sucha des1gn of furnace construction, and such improved heatdistribution, that the currents of hotter glass will be squalldistributed at looth the inner and outer sides of the refining andcooling tanks.

Another object is to provide for a deeper How of glass through the tanksystem, to avoid stagnation of the-lower strata of glass in the tanks,and also provide a longer relining period for all of the molten glassheiore it reaches the drawing machines.

Another object is the elimination of all longitudinal seams in the tankconstruction adjacent the outlet end where the refined glass flows tothe draw-pot. This eliminates one cause of cold streaks in the moltenglass supply.

Another object is to provide an improved form or air-cooled floater forproperly directing the flowing glass within the refining tank.

@ther objects and advantages will become apparent trorn the -holler-tingdetailed description oi one approved form of the turnace.

in the accompanying drawings:

Fig. 1 is a plan view 0? the entire tank construction, a portion of themelting tank losing broken away, and the heating chambers above theseveral tank portions lacing removed.

Fig. 2 is a longitudinal central section through the furnace, takensuhstmtially on the line 2+2 in Fig. l. 9%

Fig. 3 is a transverse section through the melting tank, looking towardthe two tanlzs, and taken substantially on line 3-3 of Fig. l.

Fig. l is a transverse section through one of the refining tanks and oneof the intermediate channels, looking toward the melting tank, and takensubstantially on the line H of Fig. l,

Fig. 5 is a longitudinal vertical section 190 This application is adivision of my conding application, Serial No. 671,126, filed tober 27,1923, which application issued into Patent No. 1,581,338 on April 20,1926.

The melting tank 1 is of the usual substantially rectan lar form, theglass producing materials being fed into the tank through dog-house 2,and the melting heat being supplied through suitable regeneratorsindicated at 3. The refining tanks 4 and so-called cooling tanks 5 areformed as substantial continuations of the melting tank 1, the outerwalls 6 of the refining tanks being substantially in line with the outerwalls 7 of the melting tank, although they may be flared outwardlysomewhat as at 8 to secure a somewhat greater width of refining tank.The adjacent inner walls 9 of the refining tanks are flared outwardly asat 10 near the inlet ends of the refining tanks to join with theparallel inner walls 11 of comparatively narrow channels 12 throughwhich the glass flows from the melting tank to the two refining tanks.The walls 11 are joined by a wedge-shaped wall 13 which acts to deflectthe central flow of lass from the melting tank into the two c annels 12.

Due to the cooling and frictional retarding efl'ects of the side wallsof a tank, there is always a more rapid flow of hotter glass through thecentral portions of the tank. In Fig. 1 of the drawings this flow ofhotter glass has been indicated by the procession of small arrows. Inthe-ordinary form of double tank, of the type here illustrated, thisflow of central hotter glass when divided between the two parallelrefining tanks will have a tendenc to travel along the inner adjacentsides of these tanks, and thence through the cooling chambers 5 and intothe draw-pots 14 from which the glass sheets 15 are drawn upwardly. Thiswill leave a body of nearly stagnant, and more viscid, glass along theouter sides of the refining and cooling tanks, and make it necessary toreheat the glass in the outer portions of the draw-pots or cooling tanksto obtain mobility and secure an approximately equal temperatured glassin both sides of these pots. In the present improved construction theflow of hotter glass will be divided by the wedge wall 13 and will flowthrough the relatively narrow channels 12. As in previousc0nstructi0ns,there will be a tendency for the hotter glass to flowalong the inner sides of these channels, but since the channels areoffset outwardly with respect to the center lines of refining tanks 4which they supply, the current of hotter glass will be directedsubstantially centrally into the respective refining tanks, as indicatedby the Lesa-see arrows. Also, since thesecurrents of highly mobilehotter glass are thrown outwardly by wedgemember 13'through thecomparatively narrow channels 12, they will exert a sort of sweepingaction on the outer and lower strata of glass in these channels,compelling a deeper and more complete flow of glass throu h the channelsinto the refining tanks. As t e glass stream thus composed passesthrough each respective channel into the adjoining refining tank itsvelocity is somewhat reduced as it enters the refinin tank because ofthe larger dimensions of this tank relative to the dimensions of thechannel.

At an intermediate oint in eachchannel 4, a floater 16 is positionedtransversely of the flowing glass. This floater, as shown moreparticularly in Figs. 5 and 6, is much deeper at its central portion 17.than it is at the ends 18. The end portions 18-should be only deepenough to function as shimmers for the surface lass, but should notmaterially retard the ow of glass adjacent the sides of the tank. Thecentral portion 17 of the floater projects downwardly to quite an extentinto the molten glass, so that a large portion of the centrally flowinghot glass will be diverted toward the sides of the refining tank wherean easier passage is provided. In this way the chilling and retardingeffect of the side walls of the tank are counteracted and the partialstagnation of the glass along the sides of the tank is avoided. bincethe inner adjacent walls of the refining tanks are apt to be somewhathotter than the outer walls, due to the greater opportunity forradiation loss at the outer sides of the tanks, the floaters arepositioned at a slight angle to the center line of the respectiverefining tanks, as indicated in Figs. 1 and 2, so as to divert a greaterportion of the hotter glass to the respective outer walls of therefining tank.

The retarding, and dispersal toward the tank walls, of the upper centralstratum of molten glass will give an opportunity for the lower strata,which can pass beneath portion 17 of the cooler, to pass forwardly andupwardly into the main glass stream. This movement is aided bythe'upwardly sloping bottom of the tank 4 as described hereinafter.

As shown more articularlv in Figs. 5 and 6, the preferred form offloater to be used as above described is hollow, and provided with meansfor internally cooling the floater body by passing a current of coolingfluid therethrough. The floater comprises a main body nortion 19 and acover member 20, both preferably formed of a suitable refractorymaterial such as fire-clay. A cooling fluid, such as air, is forced inthrough'a pipe 21 atone end into a longitudinal passage 22 formed in thecover member 20, and this cooling fluid is directed downwardly through aseries of flaring o enings 28 into the hollow body por tion 19 o thefloater. The air escapes through 'a passage 24 and pipes 25 at theopposite end of the cover member. Preferably, both the body member 19and the cover 20 are provided with linings of carbofrax or carborun--'dum, or other suitable non-fragile, inert and thermally conductivecomposition, as at 26 Y and 27. These linings will not be injured or yof the floater.

cracked by the direct contact of the cold air, and since the, liningsare formed of a highly conductive material they will readily transunitthe heat from the outer" clay portions of the floater body, so as tomaterially lower the temperature or" the submerged portions This willcause less expansion of the clay structure and form a protective filmcoating of chilled glass on the outside of the floater and prevent thepenetration of or the washing away of the clay body by the molten glass,thus'greatly prolonging the life of the floater, and eliminatingcontamination of the glass stream by dissolved clay, or the floatingtherein of stones of undissolved clay.

Due to the greater mass of the central portion of the floater, it willhave a greater cooling effect on the centrally flowing body of glasswhich is hottest.

After the flowing glass has passed the floater 16, the side currents ofhot glass will gradually be dispersed across the" body of the tank, andthe central flow of glass retarded by floater 16 will gradually recoverits normal flowing speed, so that a substantially even flow of equallytemperatured glass oigreater de th and width than heretofore possible,wil pass through cooling chamber 5 to the draw-pot 14.

It will furthermore be noted that the bottom wall 28 of the refiningchamber gradually slopes upwardly toward thedischarge end thereof sothat the depth of the glass, containing portion of the tank is graduallyreduced. Adjacent the dischar e end of the tank this slope is made consierably more abrupt by the angularly disposed thermally insulated blocks29 which join with the much shallower bottom portion of cooling tank 5.The tank blocks are so formed as to close ofi the lower inner corners oftank 4as at 40, where the side walls join the bottom walls. Thisfacilitates the complete flow of the glass and avoids stagnant glass inthese lower corand insure a deeper flow of glass and a-more completeemptying out of the channels, thus largely avoiding the tendency forstagnation in what would otherwise be dead portions of the tanks.

It will also be noted that the bottom and side walls of the refiningtank and cooling chamber become progressively thicker as they near thedischarge end, thereby offsetting the loss in heat by conduction andradiation to which the decreasing depth of the glass body in theseportions of the tank would otherwise be subject.

The blocks 29 and 30, forming the bottom of the discharge end of therefining tank and the cooling chamber 5, respectively, are of suchlength that they extend completely across the entire width of thesetanks. In this way all longitudinal seams or joints between blocks areeliminated. It has been found that a somewhat lower temperature prevailsalong the seams or divisions between tank blocks,

and when one of these seams runs parallel or "substantially parallel tothe flowing glass, :1

the glass stream, resulting in cords or veins in the glass sheet, or ina varying thickness of the sheet. By avoiding the use of all suchlongitudinal seams this cause for cold streaks, cords or variation inthe nature of the flowing glass is eliminated.

The melting tank 1 is enclosed by a single arched heating chamber 31from which furnace heat flows into the arched cover passages 32 overchannels 12 and thence into the arched heating chambers 33 over therefining tanks. As will be noted in Fig. 4, the outer wall 34 of chamber33 projects somewhat outwardly beyond the outer wall 6 of the refiningtank, whereas the inner wall 35 of, this chamber is substantially flushwith the inner wall 9 of the refining tank. In this way the center lineof thechamber 33 is thrown outwardly with respect to the'center'line ofrefining tank 4, so that a greater yolume of heat will be directed abovethe glass in the outer portion of the tank 4. This is to oil'set thegreater loss of heat by radiation from the outer walls of the refiningtanks. The inner walls 9, due to their prox1mity, have amutual heatingeflect and the heat loss at these sides of the tanks is not as great.The outer walls 6 of the refin= ing tanks are also preferably madethicker than inner Walls 9 to assist in retaining heat.

It will also be noted that the low-hanging arches 36 between chambers33, and the arched chambers 37 above the cooling tanks 5, are

made lower at their central portions 38 to through this chimney 39assists in cooling these inner walls and lengthens the life of thisportion of the furnace.

The general purpose ofthis improved design of: tank is toeliminate orcounteract all member being deeper at its central causes for unequaltemperatures at the inner position and viscosity is enforced through therespective tanks, thus providing a longer refining interval for anygiven portion of the molten glass. As a result, a more equally mobileand homogeneous body of molten glass is delivered to the drawots 14 fromwhich the glass sheets 15 are ta en.

I claim:

1. A continuous tank furnace, wherein the bottom of that portion of thefurnace through which the refined glass passesadjacent the discharge endof the furnace is formed of refractory blocks of a length substantiallyequal to the complete width of this portion of the tank.

2. A floater for use in a glass furnace, comprising an elongated memberof refractory clay, having an interior chamber of similar configuration,lined with silicon-carbide, and means for flowing a cooling fluidthrough the chamber. 3. A floater for use in a glass furnace, comprisingan elongated refractory member adapted to lie partially submerged in themolten glass, the member being deeper at its central portion thanadjacent its ends, and means to interiorly cool the member.

4. A member adapted for use in glass furnaces and being partially submered within the molten glass therein, said mem r having a pocket therein,and a cooler adapted to be inserted in the pocket, the walls of thecooler tapering from the top toward the bottom.

5. A floater for use in a glass furnace, including an elongatedrefractory member adapted to lie partiall submerged in the molten glass,a lining o a highly conductive material therefor, said lining snuglyfitting within the refractorymember and oeing in contact therewith, andmeans for passing a cooling medium through said lining.

6. A floater for use in a glass furnace, including an elongatedrefractory member adapted to lie partially submerged in the moltenglass, a lining of a highly conductive material therefor, and means forpassing a cooling medium through said lining, said portion than adjacentits ends.

7. A tank furnace, the bottom of a portion thereof being formed ofrefractory blocks of a length substantially equal to the complete widthof this portion of the furnace.

8. A tank furnace, including a portion through which the molten glassflows to the point of removal, the side walls of this portion of thefurnace progressively increasing in thickness in the direction ofadvance of the molten glass.

9. A tank furnace, including a portion through whichthe molten glassflows to the point of removal, the bottom and side walls of this portionof the furnace progressively increasing in thickness in the direction ofadvance of the molten glass.

10. 'A tank furnace, including a portion through which the molten glassflows to the point of removal, the bottom wall of this portion of thefurnace being inclined upwardly and progressively increasing in thicness in the direction of advance of the molten glass.

11.-A tank furnace, including a melting tank and a flow channelcommunicating therewith, and an arch member for dividing the flowchannel into two different sections, said arch member being constructedto direct more heat along the side portions of the molten glass in theflow channel than upon the central portion. I

12. A tank furnace, including a melting tank and a flow channelcommunicating therewith, and an arch member for dividing the flowchannel into two different sections, said arch member bein portion thanat its en s.

13. An arch member for use in tank furnaces and adapted to extendtransversely above the molten glass, said arch member being lower at itscentral portion than at its ends.

Signed at Toledo, in the county of Lucas, and State of Ohio, this 23rdday of March,

ENOOH T. FERNGREN.

lower at its central 8

